#include<stdio.h>
__int128_t fib_iter(__int128_t n){
    if (n<=0) n=1;
    __int128_t i;
    __int128_t fib;
    __int128_t fib1=1;
    __int128_t fib2=1;
    switch (n){
        case 1:
        case 2:
            return 1;
        default:
            for(i=3;i<=n;i++){
                fib=fib1+fib2;
                fib2=fib1;
                fib1=fib;
            }
            return fib;
    }
}
int main(){
    __int128_t n=100;
    __int128_t a=fib_iter(n);
    __int128_t b=fib_iter(n+1);
    double g=(double)a/b;
    printf("%.8f",g);
    return 0;
}